Acute Effects of Anthocyanin-Rich Blackcurrant Extract on Individual Cardiovascular and Metabolic Responses During Supine Rest and Moderate-Intensity Walking in Healthy Men

Background/Objectives: Chronic intake for 7 to 14 days of anthocyanin-rich blackcurrant extract or powder has been shown to alter cardiorespiratory and metabolic responses during rest and moderate-intensity exercise. Whether the observed effects were due to the final intake on the day of testing is not known. We examined whether there were effects of an acute intake of blackcurrant extract on the cardiorespiratory and metabolic responses during supine rest and moderate-intensity treadmill walking. Methods: Healthy men (n = 15, age: 24 ± 6 years, body mass index: 24.4 ± 4.5 kg·m−2) volunteered in a randomized, cross-over designed exploratory study. Acute intake effects of blackcurrant extract (210 mg of anthocyanins) were compared to a control condition. Hemodynamic recordings and indirect calorimetry techniques were used to record physiological and metabolic responses during 10 min of supine rest and 30 min of moderate-intensity treadmill walking. Results: At rest, there may have been an effect for an increase in cardiac output (p = 0.088). Based on the smallest worthwhile change (i.e., 0.2 × the standard deviation in the control condition), eight participants were classified as responders with an increase in cardiac output of 13.5 ± 8.4% (range: 4.0 to 24.7%). For total peripheral resistance, a decrease was observed (p = 0.048, d = −0.40, small effect size), with nine participants classified as responders with a decrease of 17.5 ± 6.1% (range: −9.7 to −28.0%). No changes were observed for other cardiorespiratory and metabolic parameters during supine rest. During moderate-intensity exercise, only heart rate was lower by 2 beats·min−1 for the cohort (d = −0.11, trivial effect size) with four participants considered responders when presenting a heart rate lower than the smallest worthwhile change of 3 beats·min−1. Conclusions: An acute intake of a blackcurrant extract with 210 mg of anthocyanins may have had an effect on vascular regulation mechanisms affecting total peripheral resistance and cardiac output during rest in at least ~50% of the male participants. No acute effects were observed for metabolic responses during rest and exercise. Our findings regarding the metabolic effects are not consistent with previous chronic dosing studies suggesting that repeated daily intake with a dose of 210 mg of anthocyanins is needed to alter substrate oxidation at rest and during moderate-intensity exercise.